|Publication number||US6879130 B2|
|Application number||US 10/715,857|
|Publication date||Apr 12, 2005|
|Filing date||Nov 19, 2003|
|Priority date||Nov 20, 2002|
|Also published as||EP1422820A1, US20040135539|
|Publication number||10715857, 715857, US 6879130 B2, US 6879130B2, US-B2-6879130, US6879130 B2, US6879130B2|
|Inventors||Yasusuke Iwashita, Takahiro Akiyama, Junichi Tezuka|
|Original Assignee||Fanuc Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Non-Patent Citations (3), Referenced by (7), Classifications (12), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a controller for performing a vector control of an induction motor.
2. Description of Related Art
There is known a method of performing a vector control of an induction motor using a rotor resistance of the induction motor. However, it is necessary to perform temperature compensation on the rotor resistance since the rotor resistance varies with the temperature. It is difficult to directly detect an actual rotor resistance or the rotor temperature in operating the motor. Thus, in order to determine the rotor resistance, there has been proposed a method of estimating the rotor temperature based on a present value or historical values of a torque current of the motor and a predetermined thermal constant such as a thermal time constant, so that the rotor resistance is determined based on the estimated rotor temperature (e.g. JP 7-67400A).
Further, there has been proposed a method of determining the rotor temperature based on a detected stator temperature, a heat conduction amount estimated using heat conduction models of the stator and the rotor, and a heat loss of the rotor, so that the rotor resistance is determined based on the rotor temperature (e.g. JP 10-23799A). Further, there is known a method of calculating the rotor temperature based on detected temperatures of the stator and ambience thereof to compensate a slip frequency based on the calculated rotor temperature (e.g. JP 1-174286A).
Moreover, there is known a method of determining a temperature compensation amount based on a detected stator temperature and a reference temperature thereof, and calculating the rotor resistance after temperature compensation based on the determined temperature compensation amount and a rotor resistance at the reference temperature, so that the slip frequency is obtained based on the calculated rotor resistance (e.g. JP 2707680B).
In the above conventional vector control of the induction motor, the rotor resistance is obtained by calculation using estimated values or models. Thus, the processing for obtaining the slip frequency is complicated since the rotor resistance is obtained by the calculation.
The present invention provides a controller for vector controlling a induction motor capable of determining a rotor resistance easily to obtain a slip frequency.
A controller of an induction motor of the present invention comprises: a temperature sensor for detecting a stator temperature; a table storing relation between the stator temperature and the rotor resistance measured in advance; and a processor to obtain a value of the rotor resistance for the stator temperature detected by the temperature sensor referring to the table, and determine a slip frequency based on the obtained value of the rotor resistance for use in the vector control.
As shown in
The excitation frequency is integrated by an integrator 6 to obtain a phase. The current conversion processing section 5 performs a d-q conversion based on driving currents of three phases detected by current detectors 10 u, 10 v, 10 w, respectively, and the phase obtained by the integrator 6, to obtain a torque current of a q-phase.
The torque current obtained by the current conversion processing section 5 is subtracted from the torque current command I2 outputted from the velocity control section 1 to obtain a current deviation to be inputted to the current control section 2. The current control section 2 performs a vector control based on the inputted current deviation, the excitation frequency and the excitation current command (not shown), to obtain a voltage command and converts the obtained voltage command into three-phase voltages to be outputted to an inverter 3 so as to drivingly control the induction motor 7.
The above hardware configuration of the controller is easily achieved by providing a general controller for performing a vector control of an induction motor with the temperature sensor 9 for detecting the rotor temperature of the induction motor 7 so that an output thereof is inputted to the slip frequency calculation section 4.
A detailed block diagram of the slip frequency calculation section 4 is shown in FIG. 2. The slip frequency calculation section 4 comprises a divider 41, a multiplier 42 and a table 43 storing information on values of the rotor resistance for the stator temperature. The torque current command (rotor current command) I2 is divided by a commanded magnetic flux Φ2 and the obtained quotient is multiplied by the value of the rotor resistance R2 read from the table 43 for the present stator temperature T at the multiplier 42, to output the slip frequency ωs. Thus, the calculation according to the following equation (1) is performed to obtain the slip frequency ωs.
ωs=(I 2/Φ2)×R 2 (1)
The table 43 stores values of the rotor resistance value R2 for the stator temperature T detected by the temperature sensor 9 based on measurements in performing operations of the induction motor 7.
Since a value of the rotor resistance R2 for the present stator temperature T detected by the temperature sensor 9 is read from the table 43, the value of the rotor resistance R2 is easily obtained to determine the slip frequency ω s.
The above processing can be performed by a dedicated circuitry but is preferably performed by a processor of the controller as software processing. The processing for calculating the slip frequency to be performed by the processor in the controller is shown in FIG. 4.
First, the torque current 12 obtained by the velocity control processing is read (Step 100), and the magnetic flux command Φ2 is read (Step 101). The stator temperature T detected by the temperature sensor 9 is read (Step 102) and the value of the rotor resistance R2 for the read stator temperature T is read from the table 43 (Step 103). The calculation according to the equation (1) using the torque current I2, the magnetic flux command Φ2, and the rotor resistance R2 is performed to obtain the slip frequency (Step 104) and the obtained slip frequency is issued for other processing, to terminate the procedure.
According to the present invention, the rotor resistance is easily obtained based on the detected stator temperature so that the slip frequency is easily and quickly determined. Since the values of the rotor resistance are predetermined based on actual measurements, the slip frequency is precisely determined to enable a precise vector control of the induction motor.
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|JPH0767400A||Title not available|
|JPH1023799A||Title not available|
|JPH01174286A||Title not available|
|JPH02211087A||Title not available|
|1||Patent Abstracts of Japan of JP 01023799 dated Jan. 26, 1989.|
|2||Patent Abstracts of Japan of JP 01174286 dated Jul. 10, 1989.|
|3||Patent Abstracts of Japan of JP 07067400 dated Mar. 10, 1995.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7423401 *||Dec 28, 2004||Sep 9, 2008||Mitsubishi Denki Kabushiki Kaisha||AC rotary machine constant measuring apparatus for measuring constants of stationary AC rotary machine|
|US7511449||Oct 31, 2006||Mar 31, 2009||Caterpillar Inc.||Electric motor system implementing vector and slip control|
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|US20050062450 *||Aug 13, 2004||Mar 24, 2005||Gary Pace||Rotor resistance estimation by calibrated measurement of stator temperature|
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|US20080100257 *||Oct 31, 2006||May 1, 2008||Speckhart Gregory J||Electric motor system implementing vector and slip control|
|U.S. Classification||318/807, 318/803, 318/811, 318/813, 318/727|
|International Classification||H02P21/00, H02P27/04, H02P21/08|
|Cooperative Classification||H02P21/10, H02P21/09|
|European Classification||H02P21/08S, H02P21/10|
|Nov 19, 2003||AS||Assignment|
Owner name: FANUC LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:IWASHITA, YASUSUKE;AKIYAMA, TAKAHIRO;TEZUKA, JUNICHI;REEL/FRAME:014729/0313;SIGNING DATES FROM 20031022 TO 20031106
|Jan 10, 2006||CC||Certificate of correction|
|Sep 24, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Sep 12, 2012||FPAY||Fee payment|
Year of fee payment: 8